Question What Makes Smoke in the Water

[Ryan Neely]

There's nothing to do with Deep Purple here; this is a legitimate question.

There's this lake my wife and I like to dive at least once a year in our neck of the woods (northern Minnesota). The particular dive site is shallow, maybe a maximum depth of thirteen feet. It's fun to snorkel, but we like to dive it to practice buoyancy and photography skills.

One particular corner of this lake always has a heavy layer of mist draping the bottom. It's right at thirteen feet of depth. If you fan away the mist, most of the vegetation beneath is black and brittle.

The lake is freshwater, so I wouldn't expect a halocline. The depth is shallow enough that the water temperature only fluctuates by a few decimal points of a degree, so I don't think its a thermocline. The lake is a flooded abandoned iron mine, though, so I wonder if there's some other chemical reaction happening here.

Once, while watching an episode of Dive Talk (I think), I watched someone dive in am abandoned mine in Missouri. The dive guide on the video indicated that metal oxidation underwater could cause things to appear to smoke, but this is a lot.

I've attached a photo of my wife near the mist for reference. The photo depicts maybe five percent of the total misty area.

Any ideas?

 

[Badger7]

I can't help with the science, but I'd love to come along for the ride on any theories. I see the same occurance at about 50-60' early in the dive season at at Lake Wazee in Wisconsin. Its a flooded iron mining quarry, and in all of the low spots on the gentle slopes there is a "mist" that develops in the larger craters, very similar to the pic in your post. Its kind of surreal looking, with the submerged sapling trunks "growing" out of the misty pools. I swept my hand through it a few times and past my mouth to see if there was any hydrogen sulfide or methane smell, and I got no indication of any strong organics, so I was just wondering if the colder pools of water drive disolved gas out of solution forming little microbubbles. If so, I can't understand why they wouldn't rise and redissolve in warmer water or rise to the surface.

 

[Divin'Papaw]

Great question. I used to see similar occurrences in the quarries I used to dive in the Midwest that had better viz. Quarries such as Gilboa Quarry near Findlay, OH. I don't recall ever hearing or learning exactly what causes this phenomenon. Looking forward to seeing what others have to share.

 

[inquis]

I would suspect some byproduct of debris decomposition which doesn't dissipate due to lack of water movement. Chemical reaction is also possible, with the notable example of a hydrogen sulfide layer, but other compounds like calcium hydroxide are possible.

 

[tursiops]

The water is not homogeneous....there can be small pycnoclines (rapid changes in the veritcal density gradient) caused by small temperature gradients, differences in salinity from rain versus runoff versus erosion, or even organics dissolved in the water. All it takes is that small, local density gradient to allow things to sink until they reach the right density, then spread out on it.